Performance requirements for gas turbine engines for commercial aircraft applications continue to be increased. The current trend in gas turbine engines is to have higher pressures and temperatures at the compressor outlet and higher rotational speeds of the compressor rotors within the engine. Because the compressor rotor speed is matched to the turbine rotor speed through an interconnecting shaft, these performance requirements also require higher rotational speeds for the turbine rotors. This trend has severely challenged the ability to provide structurally capable materials and cost effective designs that will meet these performance requirements.
Accordingly, it is desirable to improve the performance of any type of turbomachinery while limiting the required speed of the rotor portion of the turbomachine.